One of the most important requirements of the next-generation wireless communication system is to support a requirement for a high data transfer rate. To this end, research is being carried out on various technologies, such as Multiple Input Multiple Output (MIMO) and Cooperative Multiple Point transmission (CoMP), and a relay, but the most basic and stable solution is to increase the bandwidth.
However, frequency resources are now in the saturation state, and various technologies are partially being used in wide-ranging frequency bands. For this reason, as a scheme for securing a wide bandwidth in order to satisfy requirements for a higher data transfer rate, a Carrier Aggregation (CA) having a concept that each of scattered bands is designed to satisfy a basic requirement capable of operating an independent system and a number of bands are bundled into one system is being introduced. Here, a band that can be independently operated is defined as a Component Carrier (CC).
In order to support an increasing transmission capacity, in a recent communication standard, for example, a standard, such as 3GPP LTE-A or 802.16m, the extension of a 20 MHz or higher bandwidth is taken into consideration. In this case, a broadband is supported by aggregating one or more CCs. For example, if one CC corresponds to a bandwidth of 5 MHz, a bandwidth of a maximum of 20 MHz is supported by aggregating four carriers. A system using a CA as described above is called a multi-carrier system.
Meanwhile, for the purpose of efficient communication between a base station and a terminal, channel status information needs to be fed back. Channel state information fed back from a terminal and a base station can be plural according to circumstances, and one piece of channel status information can be generated and interpreted based on the other piece of channel status information. In this case, for example, the one piece of channel status information cannot be transmitted for some reasons and only the other piece of channel status information can be transmitted. Here, whether a terminal will transmit the other piece of channel status information or not using what method can be problematic. Furthermore, from a viewpoint of a base station, how the other piece of channel status information will be interpreted and applied can be problematic.